1. Field of the Invention
This invention relates to a disc loading device applied to a disc recording and/or reproducing apparatus employing an optical disc or a magneto-optical disc as a recording medium. More particularly, it relates to a disc loading device in which the above disc may be loaded on a disc table constituting the disc rotating driving device by transporting a disc transporting tray carrying the disc thereon into and out of a main body of the disc loading device.
2. Description of Related Art
There has hitherto been proposed a recording and/or reproducing apparatus in which a disc for recording information signals, such as an optical disc or a magneto-optical disc, is employed as a recording medium.
As the disc employed for such disc recording and/or reproducing apparatus, those having diameters of 12, 8 and 6.4 cm, have been proposed. Above all, the replay-only optical disc and the re-recordable magneto-optical disc, each having the diameter of 6.4 cm, is constituted as a disc cartridge by being housed within a cartridge main member as a casing, and is handled and loaded in this state into the disc recording and/or reproducing apparatus.
Meanwhile, the replay-only optical disc, on which information signals are pre-recorded and which is employed only for reproducing the recorded information signals, comprises a disc molded of a transparent synthetic resin, and a reflective layer of a metallic material deposited on one of the major surfaces of the disc substrate. The major surface of the disc substrate is formed with a pattern of micro-sized projections and recesses, corresponding to the information signals, such as by injection molding.
The information signals, recorded by the micro-sized projections and recesses, may be read by radiating a light beam to the pattern from the opposite major surface of the disc substrate, and by detecting the volume of the light reflected from the pattern.
On the other hand, the re-recordable magneto-optical disc comprises a disc substrate of a transparent synthetic resin, and a signal recording layer of a magnetic material deposited on one of the major surfaces of the disc substrate. The information signals may be recorded on the magneto-optical disc by radiating a converged laser light beam and simultaneously applying an external magnetic field to a recording track formed on the signal recording layer. The laser light beam is radiated through the disc substrate from its opposite major surface, while the external magnetic field is impressed from the firstly mentioned major surface of the disc substrate. The portion of the signal recording layer irradiated with the laser light beam loses its coercivity by being heated to a temperature higher than the Curie temperature. While being cooled, the heated portion of the signal recording layer is magnetized along the direction of the impressed external magnetic field.
That is, the information signals may be recorded on the magneto-optical disc by modulating the intensity of the light beam or the direction of the external magnetic field in accordance with the information signals, for changing the direction of magnetization of the signal recording layer as the disc is continuously rotated.
There has also been proposed a compatible disc recording and/or reproducing apparatus adapted for being selectively used with the replay-only optical disc or the re-recordable magneto-optical disc each having the diameter of 6.4 cm. This type of the disc recording and/or reproducing apparatus comprises a disc rotating driving unit for chucking and rotating the loaded disc, a magnetic head for impressing an external magnetic field to the disc driven into rotation, and an optical pickup unit for converging a laser light beam and radiating the converged beam to the disc and for detecting the return beam reflected back from the disc.
Each of the replay-only optical disc and the re-recordable magneto-optical disc has a circular loading reference opening at its center and, on its opposite major surface irradiated with the light beam, a loading height reference surface for establishing the loading height position of the disc in respect to the disc rotating driving unit.
The disc rotating driving unit, provided within the disc recording and/or reproducing apparatus, comprises a disc table for setting the optical disc or the magneto-optical disc in position in both the horizonal and heightwise directions. The disc table comprises a disc setting section integrally mounted on a spindle shaft and supporting the loading height reference surface of the disc, and a centering member provided at the center of the disc setting side of the disc setting section. The centering member is designed as an annulus having an outer peripheral surface which is tapered towards the distal end and is movably supported in the axial direction of the spindle shaft. Besides, the centering member is biased towards the distal end of the spindle shaft such as by a coil spring. As the disc is set on the disc setting section, the centering member is intruded into the loading reference opening in the disc, while it has its tapered outer peripheral surface thrust against the force of the coil spring by the inner rim of the loading reference opening in the disc, so that the disc is loaded in position on the disc table, with its center in coincidence with the center of the spindle shaft.
The magnetic head and the optical pickup unit are arranged facing each other, with the disc set on the disc table in-between, and are interconnected by a connecting arm. The magnetic head and the optical pickup unit are fed in a timed relation relative to each other in the radial direction of the disc set on the disc table across its inner and outer rims by an optical pickup feed unit, not shown.
Meanwhile, the above-mentioned disc recording and/or reproducing apparatus is provided with a disc loading device for loading the disc on the disc table.
The disc loading device comprises a disc transporting tray for holding the disc in position and for feeding the disc into and out of the main body of the device. The disc transporting tray has a disc holding recess having a size corresponding to the disc size. The disc is received within the third recess so as to be set in position. When the disc transporting tray having the disc set thereon is introduced into the main body of the disc loading device, and the disc has reached a position in register with the disc table, the disc transporting tray and/or the disc table are moved in a direction of approaching each other for loading the disc in position on the disc table.
The disc transporting tray employed in the above-described disc loading device is disclosed for example in U.S. Pat. Nos. 4,773,057 and 5,043,963. The disc transporting tray disclosed therein includes a first positioning recess for positioning a first disc having a first diameter and a second positioning recess for positioning a second disc smaller in diameter than the first disc. That is, the conventional disc transporting tray permits two kinds of discs having different diameters to be selectively positioned and held therein.
However, the conventional disc transporting tray is designed to hold only the disc itself, while it is unable to hold a disc cartridge comprising a main body of the cartridge containing the disc therein in position. Thus the disc transporting tray cannot be applied to a disc recording and/or reproducing apparatus into which a disc contained within the cartridge main body is loaded as it remains contained in the cartridge main body.